[Intel-gfx] [PATCH 37/40] drm/i915: Fix eDP link training when switching pipes

[Jesse Barnes]

On Sat, 28 Jun 2014 02:04:28 +0300
ville.syrjala at linux.intel.com wrote:

> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> When switching from one pipe to another, the power sequencer of the new
> pipe seems to need a bit of kicking to lock into the port. Even the vdd
> force bit doesn't work before the power sequencer has been sufficiently
> kicked, so this must be done even before any AUX transactions.
> 
> This sequence has been found to do the trick:
> 1) enable port with idle pattern
> 2) enable the power sequencer
> 3) proceed with link training
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 34 ++++++++++++++++++++++++++++++++--
>  1 file changed, 32 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 65ab54c..07b0320 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -2010,6 +2010,37 @@ static void chv_post_disable_dp(struct intel_encoder *encoder)
>  	mutex_unlock(&dev_priv->dpio_lock);
>  }
>  
> +static void intel_edp_init_train(struct intel_dp *intel_dp)
> +{
> +	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
> +	struct drm_device *dev = intel_dig_port->base.base.dev;
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +
> +	if (!is_edp(intel_dp))
> +		return;
> +
> +	/*
> +	 * Need to enable the port with idle pattern to allow the power
> +	 * sequencer to lock into the port. Otherwise the power sequencer
> +	 * (including vdd force bit!) doesn't work on this port.
> +	 */
> +	if (IS_VALLEYVIEW(dev)) {
> +		intel_dp->DP |= DP_PORT_EN;
> +
> +		if (IS_CHERRYVIEW(dev))
> +			intel_dp->DP &= ~DP_LINK_TRAIN_MASK_CHV;
> +		else
> +			intel_dp->DP &= ~DP_LINK_TRAIN_MASK;
> +		intel_dp->DP |= DP_LINK_TRAIN_PAT_IDLE;
> +
> +		I915_WRITE(intel_dp->output_reg, intel_dp->DP);
> +		POSTING_READ(intel_dp->output_reg);
> +	}
> +
> +	intel_edp_panel_on(intel_dp);
> +	edp_panel_vdd_off(intel_dp, true);
> +}
> +
>  static void intel_enable_dp(struct intel_encoder *encoder)
>  {
>  	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
> @@ -2021,10 +2052,9 @@ static void intel_enable_dp(struct intel_encoder *encoder)
>  		return;
>  
>  	intel_edp_panel_vdd_on(intel_dp);
> +	intel_edp_init_train(intel_dp);
>  	intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
>  	intel_dp_start_link_train(intel_dp);
> -	intel_edp_panel_on(intel_dp);
> -	edp_panel_vdd_off(intel_dp, true);
>  	intel_dp_complete_link_train(intel_dp);
>  	intel_dp_stop_link_train(intel_dp);
>  }

Yeah I think this matches the doc too.  I never pushed this change
because I could never find anything that it actually fixed.

I guess you have something now though!

Reviewed-by: Jesse Barnes <jbarnes at virtuousgeek.org>

-- 
Jesse Barnes, Intel Open Source Technology Center